In Japanese Patent Laid-open No. 8-58842, for instance, there is proposed a cushioning material for packaging making use of prismatic hollow bodies formed of a corrugated cardboard.
As shown in FIGS. 32 and 33, according to the cushioning material for packaging described in the above publication, the opposite end portions of a hollow body 6 of a square cross-sectional shape have parallel cuts 60, 61 intersecting one edge at a right angle, and an edge portion between the cuts 60, 61 has an incised portion incised in the manner of forming a plurality of symmetrical concave-convex portions 62, 63. In the body 6, two surfaces positioned with the edge between have flaps 66, 67 formed by forming folds 64, 65 to connect the opposite ends of the cuts 60, 61, and a step portion 60a is formed as shown in FIG. 33 by turning the flaps 66, 67 inward of the body 6, with the concave-convex portions 62, 63 meshed with one another.
This cushioning material for packaging is used such that the end of an article to be packaged is guided onto the stepped portion 60a and is then held therein when packaged in an outer case.
In FIG. 33, step portions 60a, 60a form a channel by combining a pair of bodies 6, 6 together to position the step portions 60a right and left, and the end of an article 4 to be packaged is guided to the inside of the channel formed by portions 60a, 60a and is then held therein when article 4 is packaged in an outer case (not shown).
Since the cushioning material for packaging proposed in Japanese Patent Laid-open No. 8-58842 described above is mainly formed of the hollow bodies 6, it has low density as a whole, but also has the following problems.
The first problem is that it is difficult to package the article 4 in the outer case together with the cushioning material for packaging, for the reason that the body 6 has only a single hollow of square cross sectional shape, so that each body 6 is easily deformed until constricted by the outer case after packaging the article 4 in the outer case.
The second problem is that only a very lightweight article can be packaged for the reason that the edges of the flaps 67, 67 constituting the bottom of the channel are connected to the flaps 66, 66 constituting the side walls only by meshing the plurality of concave-convex portions 62, 63 with one another, and a leg portion 68 in the center of the bottom of the channel mainly bears the load of the packaged article 4 so that the strength of the bottom flaps 67 is not sufficient when the above cushioning material is used in the state as shown in FIG. 33.
The third problem is that it is difficult to form the concave-convex portions 62, 63 using an automatic machining process after the hollow body 6 is formed in three dimensions. although the folds for forming the hollow body 6, the parallel cuts 60, 60, the concave-convex portions 62, 63 and the folds 64, 65 may be formed simultaneously with the process of cutting the sheet.